The present invention relates generally to magnetic resonance imaging or xe2x80x9cMRIxe2x80x9d and particularly to an apparatus and methods for entering and positioning a patient into an MRI system.
The magnetic resonance or xe2x80x9cMRxe2x80x9d scanners commonly used today require a patient who is to be scanned to be oriented with the long axis of the body in a horizontal position. This aspect of MR scanners or MRI is the result, in part, of the magnet design, the patient-positioning system used to position the patient within the magnet, and the methods designed to accommodate these features of the MRI device.
Thus, of necessity, MRI normally is restricted to the situation where gravitational force is exerted on the human body when it is horizontally oriented. However, a human body has other natural positions. These are upright or vertical positions, or sitting positions, where the forces on the body are effectively rotated 90 degrees with respect to the horizontal orientation. MR scanning of the body, oriented in a vertical or sitting position, is not presently achievable with commercially available systems.
Attempts have been made heretofore to provide MR scanning of a patient in a vertical position. For example, in U.S. Pat. No. 5,153,546, a superconductive air-core MRI magnet is shown which can be rotated by an operator so that a patient can walk into a patient receiving space within the magnet and be imaged. However, when in the patient receiving space of this reference, the patient does not have any support for sustaining and maintaining the patient""s relative orientation and position. Also, once the magnet has been rotated to accommodate a patient in a vertical orientation, there would be no room for a physician or attending personnel to access the patient during a scan. Also, if it is desirable to have a second patient scanned in a horizontal orientation, the MRI magnet would have to be rotated back to the original position by the operator. This would cause a delay before the next patient can be scanned.
Thus, it is desirable to have an apparatus and methods which would permit MR scanning to be performed with the human body oriented in a vertical or near vertical position or in a sitting position where the MRI magnet does not necessarily have to change its orientation. It also is desirable to have a patient support or rest to accommodate various orientations of the patient. Further, it is desirable to have an apparatus and methods which provide for a series of patients to be scanned in a time saving manner.
The present invention addresses these needs. The preferred apparatus and methods of this invention allow such vertical or near vertical orientation during scanning, and, most preferably, also allow other orientations of the patient. The present invention also may provide enhanced efficiency and convenience in scanning multiple patients. In addition to providing a vertical or near vertical orientation during scanning, a preferred embodiment allows a physician and associated medical personnel to have access to the patient during a scanning session so as to, by way of example, perform MRI-assisted surgery.
One aspect of the present invention provides a method of magnetic resonance imaging comprising the steps of: positioning a first patient to be scanned in a patient-receiving space of a magnetic resonance imaging magnet and conducting a magnetic resonance scan of the first patient; during the magnetic resonance scan of the first patient, positioning a second patient in a desired orientation on a mobile patient-positioning device disposed remote from the patient-receiving space; moving the first patient out of the patient-receiving space and moving the second patient into the patient-receiving space by moving the mobile patient-positioning device while maintaining the second patient in the desired orientation; and conducting a magnetic resonance scan of the second patient while the second patient is disposed in the patient-receiving space on the mobile patient-positioning device.
A further aspect of the present invention provides a method of magnetic resonance imaging comprising the steps of: positioning a series of patients on a plurality of mobile patient-positioning devices so that each patient is disposed on one associated mobile patient-positioning device which is brought to a desired orientation for that patient while the patient and the associated mobile patient-positioning device are disposed remote from a patient-receiving space of a magnetic resonance imaging magnet; moving the patients into and out of the patient-receiving space in sequence by moving the mobile patient-positioning devices so that each patient is moved into the patient-receiving space while such patient is maintained in the desired orientation; and conducting magnetic resonance scans of the patients, the aforesaid steps being coordinated so that at least some of the patients are brought to the desired orientation while other patients are disposed in the patient-receiving space.
Yet another aspect of the present invention provides a mobile patient-positioning device comprising: a frame; a patient support mounted to the frame for movement through a range of orientations relative to the frame; means for allowing movement of the frame relative to a magnetic resonance imaging magnet so that a patient on the patient support can be positioned in a patient-receiving space of such magnet with the support in any orientation. Preferably, the means for allowing movement includes wheels supporting the frame. The foregoing arrangements facilitate rapid scanning of patients in sequence. The MRI system need not remain idle while a new patient is adjusted to the proper position.
Desirably, the mobile patient-positioning device further comprises means for lifting the patient support upwardly and downwardly relative to the frame.
Alternatively or additionally, an embodiment of the present invention includes a mobile patient-positioning device in combination with an elevator mounted in a fixed location relative to the magnet, the elevator being adapted to move the frame upwardly and downwardly relative to the magnet when the frame is disposed adjacent the magnet. The arrangements allow scanning of various parts of the patient""s body.
A further aspect of the present invention provides a magnetic resonance imaging magnet comprising: a magnet frame; a pair of pole faces spaced apart from one another along a horizontal pole axis and defining a patient-receiving space therebetween; supports holding the frame on or above a floor of a structure so that a patient may enter the patient-receiving space by moving across the floor of the structure; and magnetic flux generating means for providing magnetic flux in the patient-receiving space.
Preferably the magnet may further comprise an elevator for raising or lowering a patient relative to the frame. More preferably, the elevator has a platform and the elevator is arranged to move the platform into a boarding position wherein the platform is close to the floor so that a patient standing on the floor of the structure can step onto the platform or can be wheeled onto the platform on a wheeled carriage.
In another preferred embodiment of the present invention, there is provided an MRI magnet comprising a magnet frame; a pair of pole faces spaced apart from one another along a horizontal pole axis and defining a patient-receiving space therebetween; supports for holding the frame on or above the floor of a structure so that a patient may enter the patient-receiving space by moving across the floor of the structure; and magnetic flux generating means for providing magnetic flux in the patient-receiving space; in combination with a mobile patient-positioning device. The mobile patient-positioning device includes a frame; a patient support mounted to the frame for movement through a range of orientations relative to the frame; and means for allowing movement of the frame relative to the magnet so that a patient on the patient support can be positioned in a patient-receiving space of the magnet with the patient support in any desired orientation.
Preferably, the frame is a ferromagnetic frame providing a flux return path between the poles. Desirably, the frame is generally C-shaped.
More preferably, the flux generating means is arranged to provide a magnetic field strength of at least about 3 kilogauss in the patient-receiving space.